1970 Alternator detail.

Discussion in 'Original Drivetrain Topic' started by 67johnny, Apr 8, 2021.

  1. 67johnny

    67johnny Veteran Member

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    Hey all...
    I am looking for info on the alternator fan.
    I have the correct nut,wavy washer and pulley.
    I am unsure on what is correct fan wise and if someone can let me know how many blades, color and any special marks etc. that would be much appreciated.
    Thanks.
     
  2. McCune

    McCune Veteran Member

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    11 blade, fat blade, no hook.
     
  3. COPO

    COPO Veteran Member Lifetime Gold Member

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    [​IMG]
     
  4. 67johnny

    67johnny Veteran Member

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    No Hook?
     
  5. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    There is an 11 blade alternator fan design used on other GM cars which has a "shark fin" on the ends of the blades. (Not correct)

    upload_2021-4-9_7-36-51.png


    And another design which has a hook on the "fat" blade. (Not correct)
    upload_2021-4-9_7-45-45.png

    The correct fan is the one in COPOs pic.
    It has no "hook" or "shark fins" on any of the blades.
     
  6. 67johnny

    67johnny Veteran Member

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    Much appreciated!
    I will look at the three I have and compare.
    Thanks All:bowtie:
     
  7. bkmont

    bkmont Veteran Member

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    No hooks on my 837.
    IMG_0534.JPG
     
  8. 67johnny

    67johnny Veteran Member

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    There seems to be a lot of fan choices and designs over the years.
    The one on the bottom in the pic appears to be correct.
    I am curious to know how many designs they did have available... what was the purpose of the small V notches, the one wider blade and other engineering trivia as it makes for a good read!
    The Devil is in the details they say.
    Alternator Fans.jpg Alternator fan and nuts.jpg
     
  9. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Just a guess on my part, but I have heard that they were experimenting with the blade designs due to noise. The fan spins pretty fast and can create NVH (industry parlance for noise, vibration and harshness) issues.

    Some of the "fins" I think are caused by tooling issues. The small tabs on the tips of the blades are remnants from the progressive dies used to stamp the part out of a sheet of metal. The tabs I think are used to carry the part through the die as it get formed. If the die progression (a setting in the press) changes from run-to-run it can effect the size of the tab as it is cut out at the last station in the tool where the fan is punched out.
     
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  10. 67johnny

    67johnny Veteran Member

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    I noticed that there are a lot of different stamps on these fans like the ICR or KR stamp visible in the lower pic.
    They must have had a bunch of OEM shops on the go.
     

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